Electrodeposition of nickel

ABSTRACT

A METHOD OF ELECTRODEPOSITING SATIN-LIKE FINISH NICKEL PLATES. THE BATHS COMPRISE OTHER WISE STANDARD NICKEL PLATING SOLUTIONS BUT CONTAIN THE COMBINATION OF A POLYALKYLCENE GLYCOL AND A SULFONAMIDE OF THE FORMULA   1-(HOOC-),4-(H2N-O2S-),(R)N-CYCLOHEXANE   WHERIN R IS -CH3, -C2H5, OR OH AND N IS AN INTERGER FROM 0 TO 3 INCLUSIVE.

United States Patent 3,563,866 ELECTRODEPOSITION F NICKEL Richard J.Clauss, Allen Park, Norman C. Adamowicz, Inkster, and Robert A. Tremmel,Utica, Mich., assignors to The Udylite Corporation, Warren, Mich., acorporation of Michigan No Drawing. Filed Dec. 26, 1968, Ser. No.787,271

Int. Cl. C23b 5/08, 5/46 U.S. Cl. 204-49 12 Claims ABSTRACT OF THEDISCLOSURE A method of electrodepositing satin-like finish nickelplates. The baths comprise otherwise standard nickel plating solutionsbut contain the combination of a polyalkylene glycol and a sulfonamideof the formula (IJOOH wherein R is CH -C H or OH and n is an integerfrom 0 to 3 inclusive.

THE INVENTION The invention relates to the electrodeposition of nickelon a substrate to provide a finished product whose surface has asatin-like appearance, as well as having enhanced corrosion resistanceproperties. By satin-like appearance is meant that the deposits, ratherthan being fully bright and highly reflective, exhibit a soft, lustroussheen with reduced reflectivity and gloss approaching a matte finish.

It is well known that substrates plated with semi or bright nickel,followed by an electrodeposit of chromium acquire a surface which iscorosion resistant, hard-.wearing, as well as being bright and highlyreflective. Over the years, the plating art has conducted a continuingsearch for addition agents that make possible deposits with maximumbrightness and reflectivity. In only a few applications has there been aneed for a nickel plating bath to provide electrodeposits, which ratherthan being fully bright and highly reflective, exhibit a satin-likeappearance with reduced brightness and reflectivity.

In the past, satin finishes have been used to provide a contrast withthe extremely bright nickel surface thereby giving a two-tone eifect.Recently, safety considerations.

have been a prime reason for a markedly increased interest in nickelelectrodeposits having a satin finish and decreased reflectivity.Plating baths providing such deposits are particularly useful for theplating of motor vehicle components to reduce reflective glare on thedriver of the vehicle, as well as on the operators of other vehicles. Infact, federal legislation has recently been enacted whereby certaincomponents of military vehicles such as windshield moldings and Wiperarms and blades, rear view mirrors, mounting and trim hardware, etc.,must not have a specular gloss rating beyond a stated maximum. Thus,there is an outstanding need in the art for a plating bath capable ofdepositing uniform electrodeposits having a satin appearance withreduced reflectivity.

In the past, satin finishes have been obtained by mechanical treatmentof the metal surface prior to plating, or mechanical abrasion of thenickel surface after plating by sand blasting, brush finishing, etc.This latter step not only is expensive, but also reduces the cororsionresistance of the finish because the brush or polishing marks 3,563,866Patented Feb. 16, 1971 penetrate into the plate, which is especiallydetrimental in recessed areas where the plate is thin.

A second technique to obtain satin finishes previously used has been toadd fine, bath insoluble powders to the nickel plating bath. Theparticles are occluded in the otherwise smooth nickel deposits therebyproviding an irregular surface having a lustrous, satin-like finish. Seefor example US. Patents 3,l52,97123. While such baths have providedoutstanding results, there are certain disadvantages in using suchbaths. For example, it is not possible to filter these solutions withoutremoval therefrom of the fine powders, and provisions must be made tocontinually agitate the baths to keep the particles dispersed.

An object of this invention is to provide a process forelectro-depositing nickel having a satin-like appearance without thenecessity of mechanical abrasion of the metal surface and without theuse of fine insoluble particles in the plating bath. Another object isto provide nickel plating baths containing organic agents which makepossible deposition therefrom of nickel electrodeposits having auniform, satin finish of reduced reflectivity.

The present invention comprises the conjoint use of a polyalkyleneglycol and a carboxy sulfonamide in a nickel plating bath of the usualcomposition to make possible deposition therefrom of electrodepositshaving the satin appearance described above. These baths are more easilycontrollable, provide uniform deposits, and obviate the problemsassociated with other techniques previously known for obtaining satindeposits.

The baths of the invention comprise a solution of certain organicaddition agents to be more fully described below, in otherwiseconventional nickel plating baths. The compositions of conventionalnickel plating baths are well known and include nickel salts, such asnickel chloride, sulfate, fluoborate, or sulfamate and usually contain abufler such as boric acid. A particularly useful bath is the well-knownWatts Bath with a composition of from about 50 to 200 g./l. of nickelchloride, 50 to 300 g./l. of nickel sulfate, and 30 to 50 g./l. of boricacid. The bath may also contain the usual wetting agents and/oranti-pitting agents. The baths are generally operated at a pH range of 2to 6 and a temperature of from. 60 to F.

In order to make possible the deposition of nickel of a satin-likeappearance from these baths, a number from each of two classes oforganic compounds is required.

The first class of these compounds is of the following formula:

1 )n 2 wherein X is OH2CH2O or CH;

CHOHzO R and R are the same or different and are H, CH or C H and n isan integer from 6 to 15 inclusive when X is CH CH O, and is from 5 to 11when X is CH3 -(IJHCH2O' The compounds described above are polyethyleneglycols, polypropylene glycols, methoxy and ethoxy polyethylene glycolsand methoxy and ethoxy polypropylene glycols having a molecular weightof from about 300 to about 700. A preferred group of compounds for usein the baths of this invention are compounds described above having amolecular weight of from about 350 to 500. The glycol compounds of thisinvention are used in a concentration of from about 0.25 to 15milligrams per liter, preferably 0.5 to 4 milligrams per liter ofplating bath. The polyethylene and methoxy polyethylene glycols areavailable from the Union Carbide Corporation under the trademarkCarbowax.

The second class of compounds to be used in the plating baths of thisinvention is of the following formula:

wherein R is CH C H OH, and n is an integer from O were included in theabove bath, and the plated panels were then inspected to determine if anacceptable satin appearance was obtained, with particular attentionbeing given to the uniformity of the deposits, as well as thereflectivity and gloss thereof. A tabulation of the results obtainedusing various combinations of additives is shown in Table I.

TABLE I Concentra- Brightener system tion, g./l. Results 1 i 5 3 2carboxy benzaldehyde 0.5 Ugacceptable, non-uniform, dark grey Benzenesulfonamide 2,5 dicarboxy benzene sulfonamide.

p-Carboxy benzene sulIonamide-Nacetic ac1d p-Carboxy benzene sulfonamideMethoxy polyethylene glycol, M.W. 350. 7 Polypropylene glycol, M.W. 425

eposits. 1.0 I nacceptable, non-uniform. 0. 5 Unacceptable, blackrecess. 1. Unacceptable, non-uniform. 1.0 Unacceptable, recess toobright. 0. 002 Unacceptable, non-uniform, grainy deposits 0.002Unacceptable, non-uniform deposits, dark in low current density area.

p-Carboxy benzene sulfonamide 2. ""{Polyethylene glycol, M.W. 20 0.001Unacceptable bright recess 9 p-Carboxy benzene sulfonamide" 1. 0

""""""" Polypgopylgne glycolmMW. 2%0. 010(1) Dicar oxy enzene s onaml e.d 10 "{Methoxy polyethylene glycol M. 0. 0005 gg non uniform grainy e 11{Dmarboxy benzene sulfonamlde" O Unacceptable, deposits darker andgralner i wgy p lv y s v b than Example 10,

par oxy enzene su onann e 12 "{Mtthoxy ptullyethylenenglycoht Lw. 750-0. 30% Unacceptable dark recess parboxy enzeue su onami e 13 g, g g fiifd 1 Unacceptable, bright recess par oxy enzene s onami e l 14 th glycol,350 0 0005 Acceptable, uniform; Satin like deposits 15 p-Carboxy benzenesnlfonannde 1. 0 Do Polyethylene glycol, M W 409...- 0. 003 16 p-Carboxybenzene sulfonamide" 1. 5 D o.

' Polypfiopylgne glycohllglLW. 4%5- 0. 03155 p-Car oxy enzene su onami e17 {Polyethylene glycol, M.W. 710 0. 0005 Wmmepmble, grainy 181mm In allexamples recess" refers to low current density area.

to 3 inclusive. These compounds are substituted benzene sulfonamideshaving as an essential requisite a carboxy group in the para position.The preferred compound of this group is p-carboxy benzene sulfonamide,i.e., where n is zero in the above formula. The sulfonamides are used ina concentration of from about 0.5 to about 5 grams per liter, preferably1 to 3 grams per liter of plating bath.

An outstanding benefit of the baths of the invention is that satindeposits can be obtained that are uniform in appearance over thecomplete area of the part being plated. Because commercial parts havecontours and therefore varying current densities are obtained duringplating, it is very difficult to obtain uniform deposits. Thus, whilethe use of either of the addition agents of the invention alone, or incombination with a variety of other materials may produce deposits withreduced gloss, such deposits are not uniform and therefore unacceptablefor commercial purposes. On the other hand, while it may be possible toobtain uniform deposits with such combinations, the deposits do not havethe proper gloss, i.e., they are either too dull or they approach beingfully bright, and therefore not acceptable for the purpose of thisinvention. It is only when the specific additives of the in vention areused in combination are deposits with the requisite properties obtained.

To more fully describe the invention, a series of tests are detailedbelow wherein various addition agents were added to a plating bath todetermine their effectiveness in producing nickel deposits having therequisite satin appearance. In all tests, a Watts bath having thefollowing composition was used:

G./l. NiCl 6H O 43 3 Boric acid 43 The bath was operated at temperaturesof 150-157 F. and at a pH of 3.8-4.1. Steel panels 6" x 1%", bent in theform of a I with a 1" base and 1" leg were plated for approximately 15minutes at an average current density of -45 amperes per square foot.Various additives As is apparent from the results shown in Table I, onlythe specific additives of this invention in combination make possibledeposits having the desired appeaarnce. Neither the sulfonamide compoundused alone nor the polyoxyethylene compound used alone has the desiredeffect (see Examples 5-7). However, when the compounds are usedconjointly, uniform deposits having a satin-like appearance are obtained(see Examples 14-16). This combination is very specific for the purposeintended, and when other compounds, even those structurally sirnilar tothe claimed compounds are substituted therefor the desired results arenot obtained. For example, substitution of a polyethylene materialhaving a molecular Weight outside the limits of from 300 to 700 leads topoor and unacceptable results (see Examples 8, 9, and 12). Similarly,the use of compounds structurally similar to the benzene sulfonamidegives poor results. Thus, the use of dicarboxy benzene sulfonamide(Examples 10 and ll) does not give acceptable deposits.

Optimum results are obtained by appropriate variation of significantparameters within the limits defined above. In general, it has beenfound that gloss increases with an increase in polyethylene compoundconcentration and/or bath nickel chloride content, and decreases with anincrease in carboxy benzene sulfonamide concentration, temperature andpH level. Thus, by variation of these parameters a deposit can beobtained with the desired finish for the particular application.

The baths of this invention may be used for the deposition of nickelwith a satin-like appearance on a variety of basis materials. Forexample, the plating can be carried out directly on the basis metalssuch as steel, zinc die castings, or other metals, or the basis metalmay be first plated with copper or a semi-bright nickel, or both. Also,plastic materials such as ABS or polypropylene, approximately madeconductive by conventional techniques may be plated using the baths ofthis invention.

To further investigate the properties of the baths of this invention,additional plating tests were carried out using some of the preferredadditives. The testing was carried out by plating 4" x 6" steel panelsin a 60 gallon pilot laboratory tank containing a Watts solution of thefollowing analyses:

NiCl -6H 43 g./l.

Boric Acid-43 g./l.

p-Canboxy benzene sulfonamide'1.48 g./l.

Steel panels were plated in the above solutions for 15 minutes at150-157 F., at an average current density of 30-45 amperes per squarefoot. The electrodeposits were inspected and found to be fairly uniform,but unacceptable because of a bright low current density area.

To the bath was then added methyl polyethylene glycol (sold as Carbowax350 by Union Carbide Corp.) in a concentration of 0.75 milligram perliter of solution. Five smaller steel panels were then plated under thesame conditions as the prior panel. The deposits on all five panels wereobserved to be uniform, with a soft, satin-like appearance.

The panels were then chromium plated using a conventional chromiumplating bath and then subjected to a specular gloss test in accordancewith the widely accepted A'STM method for specular glass determinationidentified as ASTM Designation: D 523-62T, revised 1962. using a GardnerGlossmeter.

With this test, light beams from a lamp are directed on the testspecimen at a specified angle and the rays reflected therefrom aredirected to a photosensitive device. Readings are then compared to aknown standard. To meet the requirements established by FederalRegulations for automotive trim parts, readings on theGardner Glossmeter(manufactured by Gardner Laboratory, Inc., Bethesda, Md.) must be below40. Readings on the five plated panels were 11, 19, 22, 10, and 12, foran average reading of 15. Thus the gloss of each of the five panels waswell within the acceptable limit of 40.

The foregoing tests were repeated under the exact conditions asdescribed above except that the concentration of the methoxypolyethylene glycol was increased to 1.0 milligram per liter. Theaverage reading on the glossmeter for the five panels was 38, just underthe maximum limit of 40. Thus, it is evident that under these conditionsa concentration of 0.751.0 milligram per liter of methoxy polyethyleneglycol is optimum to meet the automotive safety specification. Of coursefor other applications, such as furniture and other decorative systems,higher gloss readings can be tolerated and different concentrations ofthe additives, or different plating conditions may be utilized toachieve the desired level of gloss.

Deposition of the satin-nickel deposits of this invention is generallyfollowed by chromium plating thereon, using any of the chromium platingbaths well known to the art. Such baths may comprise mixtures of chromicacid or chromic acid anhydride, or dichromates or polychromates withappropriate amounts of certain anions such as sulfate, fluoride,fluosilicate, etc.

While specific benzene carboxy sulfonamides have been described, it isunderstood that the various soluble salts of these compouids such aspotassium, sodium, magnesium, nickel salts are also usable.

We claim:

1. An electroplating bath for the deposition of nickel comprising anaqueous acidic nickel salt solution containing therein a polyalkyleneglycol of the formula:

R and R are the same or different and are H, CH or C H and n is aninteger from 6 to 15 inclusive when X is --CII CH O, and is from 5 to 11when X is CH 3H-oH20- and a carboxy sulfonamide of the formula:

([IOOH wherein R is CH C H OH; and n is an integer from 0 to 3inclusive, said glycol and said sulfonamide each being present in anamount such that the combination is effective to produce a satin-likefinish nickel electrodeposit.

2. The bath of claim 1 wherein said polyalkylene glycol has a molecularweight of from about 300 to about 700 and is present in a concentrationof from about 0.25 to about 15 milligrams per liter of solution.

3. The bath of claim 1 wherein said carboxy sulfonamide is p-carboxybenzene sulfonamide and is present in an amount of from about 0.5 toabout 5 grams per liter of solution.

4. The bath of claim 3 wherein said polyalkylene glycol has a molecularweight of from about 300 to about 700 and is present in a concentrationof from about 0.25 to about 15 milligrams per liter of solution, andsaid carboxy sulfonamide is present in an amount of from about 0.5 toabout 5 grams per liter of solution.

5. (The bath of claim 4 wherein said polyalkylene glycol is apolyethylene glycol.

6. The bath of claim 5 wherein said polyalkylene gly col has a molecularweight of from about 350 to about 500.

7. A method of electrodepositing nickel on a conductive substrate whichcomprises the step of electrodepositing nickel from an aqueous acidnickel plating bath containing dissolved therein a polyalkylene glycolof the formula:

1 n Z wherein X is -CH2CI'I20 0! CH3 -oHcH o R and R are the same ordifferent and are H, CH

or --C H and n is an integer from 6 to 15 inclusive when X is CH CH O,and is from 5 to 11 when X is l S OzNHz wherein R is CH C H OH; and n isan integer from 0 to 3 inclusive, said glycol and said sulfonamide eachbeing present in an amount such that the combination is effective toproduce a satin-like finish nickel electrodeposit.

8. The method of claim 7 wherein said polyalkylene glycol has amolecular weight of from about 300 to about 700 and is present in aconcentration of from about 0.25 to about 15 milligrams per liter ofsolution.

9. The method of claim 7 wherein said carboxy sulfonamide is p-carboxybenzene sulfonamide and is present in an amount of from about 0.5 toabout 5 grams per liter of solution.

10. The method of claim 7 wherein said polyalkylene glycol has amolecular weight of from about 300 to about 700 and is present in aconcentration of from about 0.25 to about 15 milligrams per liter ofsolution and said carboxy sulfonamide is p-carboxy benzene sulfonamideand is present in an amount of from about 0.5 to about 5 grams per literof solution.

11. The method of claim 10 wherein said polyalkylene glycol is apolyethylene glycol.

12. The method of claim 11 wherein said polyalkylene glycol has amolecular weight of from about 350 to 500.

8 References Cited UNITED STATES PATENTS 2,782,155 2/1957 Du Rose et al204-49 2,784,152 3/1957 Ellis 20449 3,017,333 1/1962 Waite et al. 204493,282,810 11/1966 Odekerken 20441 3,312,604 4/1967 Wells et al 204-49GERALD L. KAPLAN, Primary Examiner

